Firefighters attempt to extinguish burning materials using extinguishing agents such as water, water with foam, or dry chemicals under a variety of circumstances. When battling structural fires in homes, commercial buildings, apartments, garages and the like it has been found that an interior attach is the most effective because the fireman can bring the extinguishing agent to the fire and apply it directly at the fuel source, thereby extinguishing the fire using a handheld nozzle. Unfortunately, conditions within a burning structure are often times hazardous and include adversities such as a complete lack of visibility beyond the firefighter's mask as a result of the smoke and other airborne contaminates produced by the blaze. Therefore, firemen rely heavily on their sense of hearing to receive communications and ascertain fire conditions.
Fires produce heat. It is generally understood that a certain minimum flow is needed to absorb this heat and extinguish a fire. This is referred to as critical flow rate. Any less flow and there is insufficient extinguishing agent to overcome the heat of combustion, while any larger flow will extinguish the blaze. Efforts to extinguish a blaze with less than the critical flow rate are a futile waste of time and a needless risk to firefighters. It is common practice for fire departments to setup standard operating procedures (SOP) to establish a desired flow for a typical fire that will insure some reasonable chance of success. The procedure generally identifies which nozzle is to be used, the diameter and length of the hose, and the pump pressure that is desired, and the physical limitations of the hose handling crew.
However, there are a number of conditions that can cause the actual flow to differ from the desired flow. The conditions include kinked hoses (which restrict flow), use of a smaller diameter hose, a longer length of hose, inattentive pump operators, fire engine malfunction, use of an inappropriately sized nozzle, or of use of a nozzle whose orifice setting differs from that prescribed in the SOP. The firefighter's safety and chance of success is compromised if the difference reduces the flow significantly. For these reasons, it is common for firefighters to pre-flow the nozzle to verify the flow before beginning the attack on the fire. During this test, a firefighter can guess if the flow of the nozzle is adequate by assessing the stiffness of the hose and the nozzle reaction force. This type of subjective judgment is not consistent or accurate, and does not insure that conditions will remain constant once the attack has commenced.
Prior art flow indicators that provide visual feedback of the flow for firemen have been in use for many years. During a fire, it would be difficult or impossible for a firefighter to see these devices not only because of the limited visibility but also because these devices would be located at the entrance of the nozzle, which is in a position near the elbow of the arm holding onto the nozzle and out of the normal field of view when one is trying to see the glow emitted from the blaze itself.
While it is certainly possible to transmit visual signals by wire, or wirelessly from a fire hose flow sensing device to a firefighter's eyes, these solutions require sophisticated electronics and result in several modes of failure. For example, a heads-up display may have its battery run low, heat or shock may damage the electronics.
Some visual indicators used spinning elements. These indicators suffered the further drawback of the indicator spinning whenever there was flow through the nozzle, and thus providing little or no assistance in determining whether the flow is not merely present but also adequate.
Attempts at providing auditory feedback have not met with success because of the inconsistent noise level from fire to fire, and because auditory feedback diminishes the firefighter's critical ability to hear other sounds on the fire scene, including communications or other sounds on the fire scene that may signal dangerous conditions.
Furthermore, nozzle-mounted flow meters and flow indicators can add significantly to the length and weight of a fire hose nozzle, thereby diminishing the firefighter's effectiveness. For these reasons, firefighters generally use flow meters and flow indicators only as training aids, and avoid them for operational use within the fire because the devices are regarded ineffective and detrimental to extinguishing the blaze.
Of the remaining human senses, it is probably not practical to use smell or taste to define when the proper flow is reached.
What is left is the sense of touch. A disposition to use the sense of touch to determine the state or position of something is referred to as haptic. Use of the sense of touch could for example include detecting force, sensing hot, cold, itchy, sharp, or painful sensations, or even sensing electric shock. Each of these sensations could be used as feedback of a flow condition.
Of these, force may be the most practical haptic sensation because many tools used by people feed back some force sensation when being operated. For example, a fire hose nozzle produces force when flow and pressure generate nozzle reaction according to the relationship of F=MA (force equals mass times acceleration). However, inasmuch as a given mass of water can be accelerated to virtually any velocity, it is not possible with present day nozzles to equate with certainty a sensed force with a specific flow. The sensation that there is some nozzle reaction does not indicate that a specific flow is being delivered, only that some flow is being delivered. The sensation of nozzle reaction force is also affected by how the nozzle is grasped, if one is in a standing, kneeling, or lying position (as firefighters are prone to do to be safe), or if one is gripping the nozzle with bare hands or with full bunker gear and thick firefighter's gloves. Detecting a specific force is also a function of memory and experience, which are not always available, consistent, or reliable.
The sense of touch may also be used to detect a repetitive force, as might result from use of a jackhammer, jigsaw, or vibratory sander, or pneumatic ball vibrator. However, none of these vibrating devices have been employed to provide haptic feedback to a firefighter to indicate that a desired magnitude of water flow is being delivered.
What is desired then is a device that emits a haptic signal to a fireman that can be used to detect when a flow of water of a specific magnitude is achieved.